This invention relates to a double walled hose assembly. More particularly, the invention relates to a double walled hose assembly used in a fluid supply system to convey hazardous fluids.
While the invention is particularly applicable to double walled hose assemblies used in the petroleum, chemical and natural gas industries, it should be appreciated that such a hose assembly can be utilized in connection with any type of installation in which leakage of a hazardous fluid into the surrounding environment over long periods of time and without detection will produce extensive pollution and an environmental hazard. Such pollution is likely to be difficult and expensive to clean up when it is ultimately found.
A conventional underground fluid piping systems such as is utilized in, e.g. a service station environment, is typically made of steel, fiberglass or plastic. Such systems include rigid straight lengths of pipe together with T-fittings, elbows, connector fittings, union fittings and the like. The assembly of these components creates a fluid piping system with many joints and typically a layout design that has many turns in congested plumbing areas. Since the primary source of leaks is at the joints and fittings of a system, such systems are prone to leakage. In addition, the many fittings are adversely affected by ground movement during the life of the fluid system as well as by improper installation and environmental degradation such as corrosion.
In response to environmental regulations and ever stricter pollution control requirements at the federal, state and local levels, strict regulations have been implemented for underground piping which transmits hazardous fluids. Equipment manufacturers have responded by developing a variety of secondary containment systems for conventional underground piping. Such containment systems are designed to prevent the fluid that may leak from the inner pipe or hose from escaping into the environment. One approach for such a secondary containment system has been to line the piping trench for the hose with a flexible membrane liner or a semi-rigid trough. While such an approach provides a measure of containment of the leaking product, it does not allow for effective leak detection because the location of the leak cannot be easily determined. Also, an integrity check of the secondary containment system by means of air pressure testing and the like is not possible since the system does not provide a 360.degree. containment of the leaking fluid.
Another approach has been to utilize a rigid larger diameter pipe to enclose the conventional fluid rigid supply pipe. However, these types of secondary containment systems are generally expensive and time consuming to install. Also, the outer pipe is prone to leakage as is the product supply pipe. Still another approach has been to encase the rigid product supply pipe with a larger diameter convoluted, and therefore flexible, plastic pipe that contains not only the rigid product pipe but also several of the fittings for the product pipe. However, this type of containment system is still expensive and one cannot identify the location of a leak in the product pipe.
Still another recent suggestion has been to provide a secondarily contained piping system in which a flexible supply pipe is positioned within a rigid corrugated secondary containment pipe. With this type of system, once a leak has been identified in the fluid supply pipe, the length of that pipe in which a leak has occurred can be removed from an underground location through an access chamber after the pipe is uncoupled from adjacent sections of the pipe. The leaking section can then be replaced with a new length of pipe. However, this proposal is difficult to employ in practice since the fluid supply pipe is resistant to the type of bending necessary to pull it out of the secondary containment pipe. In addition, necessarily, a large diameter secondary containment pipe is required in order to allow one to try and pull the fluid supply pipe out of the secondary container pipe once a leak has been detected. Also, this system does not positively identify the location of the leak.
Accordingly, it has been considered desirable to develop a new and improved double walled hose assembly which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.